Vehicle would lock all doors normally by remote and by the master door lock switch, but would not unlock any of the four doors by remote or by the internal door locking switch.

Confirmed the vehicle had a no-unlock fault affecting all doors. Lock command operated correctly, but unlock command did not. There was no indicator flash on unlock when the doors were locked, although the indicators would flash if the vehicle was manually unlocked first and then the remote was pressed. This indicated the unlock side of the central locking control circuit was at fault rather than a problem with the remote programming or the door actuators themselves.